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排序方式: 共有246条查询结果,搜索用时 15 毫秒
101.
Ayhan MM Singh A Hirel C Gürek AG Ahsen V Jeanneau E Ledoux-Rak I Zyss J Andraud C Bretonnière Y 《Journal of the American Chemical Society》2012,134(8):3655-3658
The concept of octupolar molecules has considerably enlarged the engineering of second-order nonlinear optical materials by giving access to 2D and 3D architectures. However, if the archetype of octupolar symmetry is a cube with alternating donor and acceptor groups at the corners, no translation of this ideal structure into a real molecule has been realized to date. This may be achieved by designing a bis(phthalocyaninato)lutetium(III) double-decker complex with a crosswise ABAB phthalocyanine bearing alternating electron-donor and electron-acceptor groups. In this communication, we present the first step toward this goal with the synthesis, crystal structure determination, and measurement of the molecular first-order hyperpolarizability β by harmonic light diffusion, of an original lutetium(III) sandwich complex displaying the required ABAB-type alternation for one face of the cube. This structure is characterized by an intense absorption in the near-IR due to an intervalence transition and exhibits the highest quadratic hyperpolarizability ever reported for an octupolar molecule, √<β(2)(HLS)> = 5750 × 10(-30) esu. 相似文献
102.
103.
Exact Solutions for Fractional Differential-Difference Equations by (G′/G)-Expansion Method with Modified Riemann-Liouville Derivative 下载免费PDF全文
Ahmet Bekir Ozkan Guner Burcu Ayhan & Adem C. Cevikel 《advances in applied mathematics and mechanics.》2016,8(2):293-305
In this paper, the ($G′/G$)-expansion method is suggested to establish new
exact solutions for fractional differential-difference equations in the sense of modified
Riemann–Liouville derivative. The fractional complex transform is proposed to convert
a fractional partial differential difference equation into its differential difference
equation of integer order. With the aid of symbolic computation, we choose nonlinear
lattice equations to illustrate the validity and advantages of the algorithm. It is shown
that the proposed algorithm is effective and can be used for many other nonlinear
lattice equations in mathematical physics and applied mathematics. 相似文献
104.
Zeliha Erbas Sadin Ozdemir Ersin Kilinc 《International journal of environmental analytical chemistry》2013,93(11):1112-1122
ABSTRACTIn this study, preconcentration and separation of Cu(II) and Pb(II) ions by using Fe3O4@SiO2@Bacillus pumilis before their determinations by flame atomic absorption spectrometry (FAAS) were investigated. The thermophilic Bacillus pumilis were isolated from Meyremderesi spring, ??rnak, Turkey. Effects of important parameters such as pH, adsorbent amount, eluent type, concentration and volume of eluent and sample volume on magnetic solid phase extraction (MSPE) were examined in details. The preconcentration factors for Cu(II) and Pb(II) ions were calculated as 30 and 40, respectively. The accuracy of the proposed extraction procedure was validated analysing certificated reference materials and addition – recovery tests. The concentration of copper and lead were determined in water samples from Turkey by Flame AAS after application developed preconcentration-separation method. 相似文献
105.
A novel proton conducting polymer blend was prepared by mixing poly(vinylphosphonic acid) (PVPA) with poly(1-vinylimidazole) (PVI) at various stoichiometric ratios via changing molar ratio of monomer repeating unit to achieve the highest protonation. The polymer network having the most suitable stoichiometric ratio for substantial proton conductivity was prepared and characterized by FT-IR spectroscopy and proton conductivity measurements. The network was used for immobilization of invertase and some important kinetic parameters such as the maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were investigated for the immobilized invertase. Additionally, optimum temperature and pH were determined to acquire the best conditions for the highest enzyme activity. Operational stability of the entrapped enzyme was also examined. The results reveal that the most stable and highly proton conducting polymer network may play a pioneer role in the biosensors applications as given by FT-IR, elemental analysis, impedance spectroscopy and storage stability experiments. 相似文献
106.
Ozlem SevenSidika Polat-Cakir Md. Shakhawoat HossainMustafa Emrullahoglu Ayhan S. Demir 《Tetrahedron》2011,67(19):3464-3469
The reactions of organoaluminum reagents (trimethylaluminum, triethylaluminum, etc.) with aryl and alkyl acyl phosphonates, which lead to the formation of α-hydroxy phosphonates in moderate to good yields, are reported. This method provides easy access to secondary and tertiary α-hydroxy phosphonates depending on the reaction conditions. The reactions of triethylaluminum with a series of acyl phosphonates at 0 °C gave the secondary α-hydroxy phosphonates, while at −100 °C they afford the tertiary α-hydroxy phosphonates. 相似文献
107.
[reaction: see text] Benzaldehyde lyase from the Pseudomonas fluorescens catalyzes the reaction of aromatic aldehydes with methoxy and dimethoxy acetaldehyde and furnishes (R)-2-hydroxy-3-methoxy-1-arylpropan-1-one and (R)-2-hydroxy-3,3-dimethoxy-1-arylpropan-1-one in high yields and enantiomeric excess via acyloin linkage. Aromatic aldehydes and benzoins are converted into enamine-carbanion-like intermediates prior to carboligation. 相似文献
108.
The gamma-irradiated single crystals of 2-Bromo-4′-methoxyaceto-phenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA. 相似文献
109.
Celik SU Akbey U Graf R Bozkurt A Spiess HW 《Physical chemistry chemical physics : PCCP》2008,10(39):6058-6066
The synthesis, thermal and proton conducting properties of copolymers based on vinylphosphonic acid (VPA) and 1-vinyl-1,2,4-triazole (VTri) were investigated. The copolymers were synthesized by free-radical copolymerization of the corresponding monomers at several monomer feed ratios to obtain poly(VPA-co-VTri) copolymer electrolytes. The final structures of the copolymers were confirmed by spectroscopic methods. The composition of the low molecular weight copolymers was varied with the feed ratio of the monomers. The presence of triazole units in the copolymers suppresses the formation of phosphonic acid anhydrides up to 150 degrees C, as verified by both (31)P NMR and TGA. The observation of defined glass transition temperatures indicated that the ionic interactions do not prevent segmental relaxations of the polymer chains. In the absence of humidity, the copolymer electrolyte, poly(VPA-co-VTri), S2 (with 33% triazole content) showed proton conductivity of 10(-3) S cm(-1) at 120 degrees C, which is far higher than in imidazole based copolymers. Two different types of hydrogen-bonded protons were detected by (1)H MAS NMR in the solid copolymer systems, due to different arrangements of triazole and phosphonic acid units. 相似文献
110.
Long-chain N-alkyl-2-(phenylthio)acetohydrazides were synthesized via the reactions of 2-(phenylthio)acetohydrazide with long-straight-chain aldehydes and then reduction with sodium borohydride.
The reactions of long-straight-chain hydrazides with carbon disulfide in alkaline media give the corresponding carbodithioate
salts. Heating of potassium 2-alkanoylhydrazinecarbodithioates with phenacyl bromide do not yield cyclization and failed to
give the corresponding long-chain thiazolidine-2-thiones, but gave the corresponding 2-oxo-2-phenylethyl-2-alkanoylhydrazinecarbodithioates
via nucleophilic substitution reaction. In addition, the synthesized compounds were tested for their corrosion prevention capabilities
in acidic or in mineral oil media.
Correspondence: Ayhan Yıldırım, Department of Chemistry, Faculty of Science and Arts, Uludağ University, 16059 Bursa, Turkey. 相似文献